Silicon is a commonly used semiconductor material for commercial applications, and a majority of commercial electronic devices and solar cells are based on silicon. Most consumer electronics comprise silicon based circuits, and flat panel displays can comprise large area circuits to drive the display. Several solar cell designs based on silicon can be used, and most commercial solar cells are based on silicon. The formation of functional devices generally involves doping the silicon to control the electrical and conductive properties.
Photovoltaic cells are an important alternative energy source with growing global use. Generally, photovoltaic cells operate through the absorption of light to form electron-hole pairs within a semiconducting material. Oppositely doped regions within the photovoltaic cell provide a junction with the individual doped regions forming contacts for the separate collection of holes and electrons, which results in a voltage differential that can be used to drive a photocurrent. The photocurrent is available to perform useful work in an external circuit.
Solar cells based on crystalline or polycrystalline silicon provide particular design considerations. For solar cells with crystalline or polycrystalline silicon layers, localized doped contacts can be used to assist with the collection of the photocurrent. Current collectors generally are then in electrical contact with the doped contacts to provide for connection of the solar cell to an external circuit. Doped contacts with opposite dopant types can be placed on the front and back of the solar cell. In alternative designs, all of the doped silicon contacts of the solar cell are placed on the back side of the cell to form a back contact solar cell. With a back contact solar cell, the front, light receiving surface can be free of current collectors.